front suspension work

[Clutch]

I'm getting ready to replace the front suspension springs and fork oil seals.  I was going to do this tomorrow, but after looking through the procedure in my Clymer's I notice that there are a few other parts that I probably should replace: 1)wiper ring on the damper piston (figure 244, page 515 of Clymer's) 2) stop ring and washer (fig. 251, p. 517 of Clymer's).

Question 1:  Does anyone know of any other parts that can be expected to have degraded inside the forks (plastic, rubber parts, etc.)?  I don't think the suspension has ever been taken apart before.

Question 2:  I can't find a part number for the wiper ring on the damper piston (can't find a part number for the whole damper piston, for that matter).  All the parts fiches that I've looked at includes it with the "absorber".  Can anyone else figure this out?

thanks

[Justin B.]

I have never replaced any of that internal stuff.  The last time we had the forks apart on the '80 we replaced the fork seals and popped in new springs.  They feel fine...

[Bob_Roller]

What sites have you looked at ? I've been using RealOEM.com, you need the last 7 characters of the bikes VIN to do a search of your bike specifically.

[Ed Miller]

There's nothing on the absorber that needs to be replaced, unless you take the front end apart and see something broken.  The bolt that holds that stuff onto the damper rod is red locktited anyway.  Unless you have a million miles on the bike I doubt those little piston like scraper things are worn.  

There are little white (they start life that way, anyway) thick rubber rings at the bottom (31 42 1 237 215), and I think some other gasket down there too but I'm not sure.  Maybe I'm just thinking of the crush washers for the bottom bolt.

Are you getting the parts mail order?  If so it would be easy to call, say, Boxerworks and ask what else might be worn in there.  

[Clutch]

bob roller:  I've looked at realoem and maxbmw parts fiches, and they are basically the same.  I've never seen a place to put in the vin number.  I've just gone through the drop-down menus to choose the model/year/month made.

ed:  From the clymers, it looks like there is an o-ring (called "wiper ring" in clymers) that fits in a groove on the damper piston (the screw-on piece at the top of the absorber).  Is this not an o-ring?  Also, I was planning on replacing that white washer (stop ring) at the bottom of the absorber too.  I hadn't thought about calling Boxerworks, but I am going to call Bob's BMW this morning to see if they can help me out.

thanks!

[Ed Miller]

OK, so I dug out my Haynes (don't have a Clymer).  Are you sure you're looking at the R65 diagram?  Mine doesn't show any wiper rings, but it also shows the damper rod as one unit just like my ETK program.  I see wiper rings for the /5, 6, and 7 front forks.  I think they are probably the same as the little piston type rings that I mentioned earlier, that are installed on the damper rod.  I'm not sure what they do, but they are springy steel and would take a long time to wear out.  If they are broken somehow, that would be a different matter, but you shouldn't have to disassemble the damper rod at all.  You have to use thin bits of metal like feeler guages to get the damper rod wiper rings to compress back into the stantion when you reassemble things.  (Don't use feeler guage sizes that you need for anything else!)  Haynes has a picture of how to do that.

There is an o ring that goes on the top fork plug, part number 31 42 1 237 245 that you should probably replace; I missed that one before.

Good luck!

[Clutch]

good man Ed!    I squinted at the photo in clymer's and it does look like metal rings on the damper piston instead of an o-ring (so I'm not going to worry about it).  I'll be sure to get some of those o-rings for the top fork plugs too.

The main reason why I'm worrying about this is because I have to bring my bike over to a friend's to work on it, and he has to clear out all his motorcycles so I can work on mine.  I just need to be well prepared to be able to replace anything that I can expect to need replacing, since I can't leave it in his garage.  I really appreciate your effort Ed.

[Ed Miller]

I get you.  Stuff like that is the main reason I'm reluctant to do much on my own bike at a tech day at somebody else's house.  I did go through my front forks at the first tech day I ever attended, in Salem, but I brought the parts over in saddle bags on my Triumph.  It was good to have help getting those damper rods into my new stantions, that's like a 3 hand job!

Hope it all goes well!

 [smiley=beerchug.gif]

[Justin B.]

It does make it much easier to have a helper.  The Kid and me had it down pretty good after a couple teardowns.  I put an allen bit on a long extension with a "T" handle on top - this he leaned on to depress the plunger and while it was depressed I popped in the circlip.  I have read about folks that fabricated a depressor tool that they could screw down, depressing the plunger, and install circlip with no muss.  I can envision maybe a piece of angle-iron or "U" channel bolted across the handlebar holes with a nut welded over a hole at the right spots on each end.  One could bolt this contraption on, screw a long bolt through each end depressing the plungers - as long as there was still room to get fingers in to pop in the clip.

[Chris_in_BC]

Question 2:  I can't find a part number for the wiper ring on the damper piston (can't find a part number for the whole damper piston, for that matter).  All the parts fiches that I've looked at includes it with the �absorber�.  Can anyone else figure this out?

thanks

Parts catalogues never seem to show a rebuild kit for post 1981 forks like they did for earlier bikes. But the 3 damper rings are the same as on earlier forks. I ordered some from Moto-Bins  a while back.

Chris

[Clutch]

That's good to know about the wiper rings, Chris.  I'll be sure to tell the parts person that if they don't know what they are doing.  I was hoping I could find a suspension rebuild kit online, but have been unsuccessful.  I haven't been able to call any place yet, as I've been constantly busy with school stuff the past 2 days.

thanks man

[nhmaf]

I'd also recommend that you get new crush washers for the bottom allen-head bolt, and for the drain
plugs.   Having taken my fork all apart and replacing springs and seals - it was disappointing to
go for a ride and come bike with hydraulic oil all over my front brake rotors.   Had to replace
pads, drain and take the forks off again all to replace those little washers that had leaked.  BMW
recommends replacing them everytime, though you often don't have to - but those flimsy metal
washers will only take so much deformation before they won't seal tight anymore.   For the lack
of some 15 penny washers, I had alot more expense and headache !

 

[Ed Miller]

Oh, they'll seal all right, but you have to jam the bolts down so tight you strip the threads.

...at least, that's how it theoretically works out in my head, I of course wouldn't know from real life.

[Justin B.]

The ones I was sent last time I ordered were aluminum.  I guess BMW figured out that the copper ones last through multiple teardowns and this was a way to make a few extra bux!   If yours are aluminum then replace...  Also make sure you have a looong extension and a 12 (or is it 13?  CRS kicking in again) mm socket on hand when tightening.  My experience is about 50% of the time you will need to go down into the fork tupe with this to keep things from turning as you tighten the lower allen bolt.  [smiley=1drink.gif]

[Clutch]

Thanks all.  I had the crush washers figured into my order.  I wonder if you could go to a hardware store and find some copper ones that would last longer and do just as well?  Eh, I'm not gonna worry about it - I'll just get the aluminum ones and be happy.

Regarding the socket and long extension:  thanks for the heads up.  I always seem to cuss less when I expect something to be a pain in the a*s, compared to when it hits me by surprise.  However, cussing is required during most of my maintenance tasks.